Reception head for a filter unit

ABSTRACT

The invention relates to a mechanical support for a drainage device of a filter unit for microbiological testing of liquid substances. Said filter unit is provided with a membrane and adapted to be mounted on said mechanical support so that said membrane faces a reception surface of said mechanical support. The mechanical support comprises: a passage one end of which discharges externally of said reception surface and the other end of which discharges internally said reception surface; and selectively operable means for closing said passage, movable between a first position in which they close said passage and a second position in which they open said passage.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Stage Application of InternationalApplication No.: PCT/2003/005110, filed on Oct. 24, 2003, which claimspriority to French Application No.: 0213483, filed on Oct. 28, 2002.

The present invention relates to a mechanical support for a drainagedevice of a filter unit for microbiological testing of liquidsubstances.

Said filter unit is provided with a membrane on which the microorganismscontained in the liquid substance are concentrated during drainage.

The membrane is then placed in an agar culture medium to encourage thegrowth of said microorganisms.

There are prior art drainage devices which avoid contaminating a liquidsubstance to be analyzed by forcing a sample of the liquid substancethrough a membrane by creating a reduced pressure on the downstream sideof the membrane.

In devices of the above kind a vacuum pump is generally connected to aflask to create a reduced pressure therein and a receptacle closed atthe bottom by said membrane is mounted directly on the flask. Thanks tothe suction induced by the reduced pressure, the liquid substance samplecontained in said receptacle is aspirated into the flask and themicroorganisms are held back by the membrane.

Improved devices include a mechanical support that has a receptionsurface, and the filter unit is mounted on and sealed to said mechanicalsupport so that said membrane and said reception surface form a suctionchamber.

A drawback of the above devices is the manner of mounting the filterunit on the mechanical support, which traps and compresses air betweenthe membrane and the reception surface, which can cause the membrane toburst.

Moreover, after the liquid substance has been filtered, residualquantities, which are difficult to evaporate, remain in the suctionchamber and moisten the membrane. The microorganisms then tend todiffuse on the culture medium.

A problem that arises and that the present invention seeks to solve isthat of providing a mechanical support such that the membrane isprotected during mounting and dried after filtration.

To this end, the present invention proposes a mechanical support for adrainage device of a filter unit for microbiological testing of liquidsubstances, said filter unit being provided with a membrane and adaptedto be mounted on said mechanical support so that said membrane faces areception surface of said mechanical support,

which mechanical support is characterized in that it comprises:

-   -   a passage one end of which discharges externally of said        reception surface and the other end of which discharges onto        said reception surface; and    -   selectively operable means for closing said passage, movable        between a first position in which they close said passage and a        second position in which they open said passage.

Accordingly, one feature of the invention is the provision of a passagethat is connected to the interior of the suction chamber and dischargesto the exterior of the reception surface, for example to the atmosphere.As a result, when the filter unit is nested over said mechanicalsupport, the selectively operable closure means are driven into saidsecond position to open said passage and air trapped between themembrane and the reception surface, forming the suction chamber, escapesvia the passage and is therefore not compressed against the membrane.

As explained in more detail hereinafter, said passage is also kept openwhen said filter unit is removed, to prevent deterioration of themembrane.

The passage is kept closed during filtration, of course.

In one particularly advantageous embodiment of the invention, saidselectively operable closure means comprise a valve adapted to slide ina bore which said passage crosses, said bore discharging onto anexternal surface portion of said reception head to drive said valve intranslation between said first position and said second position.

Accordingly, thanks to this feature, the passage is easily opened orclosed by operating the valve from outside the head.

In one particular embodiment of the invention, the mechanical supportcomprises a suction duct that discharges onto said reception surface toaspirate a liquid substance contained in said filter unit through saidmembrane.

Accordingly, after all of the liquid substance contained in the filterunit has been filtered and aspirated, because the membrane is relativelyimpermeable to air, it cannot be dried by the small amount of air thatpasses through it and is drawn into the suction duct.

The valve is then moved to the second position, to open the passage, andexterior air is aspirated from the outside of the mechanical support,passes through the passage, and then flows into the suction chamber,from which it is evacuated via the suction duct.

As a result, thanks to the passage, the membrane is dried with sterileair coming from the environment of said mechanical support, which ishoused in a hood, for example, or in the vicinity of the flame of aBunsen burner. The resulting dried membrane ensures improved growth ofthe microorganisms when the membrane is placed on the nutrient medium.

Moreover, because filter supports are difficult to disinfect, not alltypes of filter unit can be fitted to a particular mechanical support.

To solve this problem, in another particularly advantageous embodimentof the invention, the mechanical support comprises:

-   -   a reception head adapted to receive said filter unit and        including said reception surface, said passage, said selectively        operable closure means, and first connecting means; and    -   a head support including second connecting means, said reception        head being adapted to be mounted on said head support so that        the first connecting means and the second connecting means        cooperate with each other.

Accordingly, not only is the reception head adapted to be replaced byanother reception head adapted to receive another type of filter unit,which might have greater volume capacities, for example, or differentkinds of filter, but it is also adapted to be sterilized in an autoclaveor by immersion in a sterile solution, for example, independently of theother components of the mechanical support. As a result, the receptionhead is perfectly sterile and contamination of the membrane of a filterunit during a new series of analyses is totally avoided.

Said reception head advantageously has a cylindrically symmetric openingformed in the portion opposite said reception surface to form said firstconnecting means and said head support has a substantially verticalprojecting portion forming said second connecting means and adapted tocooperate with said opening when mounting said reception head on saidhead support

Thus the various reception heads all have an opening of the same sizethat is identically located in the portion opposite the receptionsurface so that it can be mounted on the head support, said verticalportions being engaged in said opening.

Said reception head and said head support preferably include keyingmeans for locking said connecting means. Thus the reception head isretained in a fixed position on said head support.

In another particular embodiment of the invention, said reception headhas a transverse bore adapted to cooperate with a groove formed aroundsaid vertical portion, said transverse bore being adapted to receive keymeans for forming said keying means.

As a result, the transverse bore which intersects said opening formed inthe reception head is adapted to receive key means that are mobile intranslation in said bore. The key means are withdrawn from the bore whenthe reception head is engaged on said head support and are thenreinserted to pass through said bore and a portion of the groove in saidvertical portion. Thus the reception head is prevented from moving invertical translation relative to said head support.

It is particularly advantageous if said head support includes a suctionbranch whose first end is adapted to be connected to said suction ductof said reception head and whose second end is adapted to be connectedto a suction pump.

The reception head includes the suction duct through which the liquidsubstance is aspirated and the head support includes a suction branchadapted to be connected to said suction orifice in order to aspirate theliquid substance by means of the suction pump. Accordingly, the suctionorifice of each reception head must be connected to the first end of thesuction branch in a substantially sealed manner in order to be able tocollect the liquid substance without leaks of air or liquid substance.

Said head support preferably includes a driver device adapted to take upa position opposite said external surface portion and to bear againstsaid valve to drive it in translation into said first position or intosaid second position.

Accordingly, thanks to this feature, the valve is adapted to be drivenfrom the exterior of the reception head.

According to one advantageous feature, said driver device includes asolenoid whose core is adapted to drive said valve. As a result, thevalve is easy to operate with a simple electrical contactor.

In another aspect, the present invention proposes a reception headcomprising:

-   -   a passage one end of which discharges externally of said        reception surface and the other end of which discharges into        said chamber;    -   selectively operable means for closing said passage, movable        between a first position in which they close said passage and a        second position in which they open said passage;    -   a cylindrically symmetric opening in the portion opposite said        reception surface; and    -   a transverse bore adapted to cooperate with said opening, said        transverse bore being adapted to receive key means.

Other features and advantages of the invention will emerge from areading of the following description of particular embodiments of theinvention, which are provided by way of illustrated but nonlimitingexample, which description is given with reference to the accompanyingdrawings, in which:

FIG. 1 is a diagrammatic view in vertical section of one particularembodiment of the subject matter of the invention;

FIG. 2 is a diagrammatic view in vertical section of the subject matterof the invention as shown in FIG. 1 in a particular position;

FIG. 3 is a diagrammatic view in vertical section showing animplementation of the subject matter of the inventions-shown in FIG. 1;

FIG. 4 is a view in section taken along the line IV-IV in FIG 2;

FIG. 5 is a diagrammatic view in vertical section taken along the lineV-V in FIG. 4 of a detail of another particular embodiment of theinvention;

FIG. 6 is a diagrammatic view in vertical section taken along the lineVI-VI in FIG. 4 of said other particular embodiment of the invention;and

FIG. 7 is a diagrammatic perspective view of said other particularembodiment of the subject matter of the invention.

FIG. 1 shows a mechanical support 10 according to the inventionincluding a head support 12 and a reception head 14 having a receptionsurface 16 from which extends an suction duct 18 that is extended by ansuction branch 19. The mechanical support 10 shown in vertical sectionin this figure is a circular cylinder whose axis of symmetry is in theplane of the figure.

Moreover, the reception surface 16 is circular and the suction duct 18discharges at its center.

The reception head 14 includes a passage 20, one end 22 of whichdischarges externally of the reception surface 16 and externally of thereception head 14 and the other end 24 of which discharges onto thereception surface 16. In FIG. 1, the passage 20 is closed by a valve 26in a first position, the valve consisting of a piston in which a groove25 is provided to form the valve. The valve 26 is mobile in verticaltranslation in a bore 27 through which said passage passes, said bore 27discharging at one end onto an external surface portion 29 of thereception head 14. The other end of the bore 27 includes a circular sealprojecting from the internal surface of the wall of the bore, whichforms a valve seat 31 against which the valve head 26 is bearing in FIG.1.

The head support 12 includes a driver device 28 formed of a solenoidinside which a core is extended by a punch 30. The driver device 28 isdisposed opposite the external surface portion 29 so that the end of thepunch 30 is in the bore 27 in the vicinity of the external surfaceportion, the axis of said punch 30 being substantially parallel to thebore 27.

As a result, when the solenoid 28 is operated, the punch 30 is adaptedto drive the valve 26 in the direction of the arrow T to open thepassage 20, as shown in FIG. 2.

Moreover, the valve 26 includes a return spring 32 adapted to drive itinto the first position when the solenoid 28 is no longer energized, sothat the punch 30 returns to its original position.

Refer now to FIG. 2, which shows the mechanical support according to theinvention in vertical section and in which can be seen the mechanicalsupport 10 and the driver device 28 whose punch 30 actuates the valve 26housed in the reception head 14, with the valve in a second position inwhich the passage 20 is open.

In this second position, the valve head 26 is disengaged from its valveseat 31 with the result that the groove 25 establishes communicationbetween the end 22 of the passage that discharges externally of thereception head 14 and the end 24 of the passage 20 that discharges ontothe reception surface 16.

FIG. 1 also shows a filter unit 34 which includes a membrane 36 which isadapted to face the reception surface 16. The filter unit 34 is adaptedto receive a liquid substance to be filtered, the filtrate beingaspirated through the membrane 36 and into the suction duct 18.

The membrane 36 is fastened to the filter unit 34 and is separated fromthe reception surface 16 by a sterile separator 38 consisting of a gridapproximately 0.5 mm thick, to prevent it from coming into directcontact with the reception surface 16.

The base 40 of the filter unit 34 and the reception head 14 aresubstantially frustoconical in shape, for improved centering and to sealthe junction between them.

The membrane 36 is relatively impermeable to air, whether dry or moist.Accordingly, when the filter unit 34 is fitted to the reception head 14and they form a suction chamber between the membrane 36 and thereception surface 16, the air trapped between the two can escape via theopen passage 20.

In the same way, a reduced pressure is created in said suction chamber,between the membrane 36 and the reception surface 16, when the filterunit 34 is removed from the reception head 14, and the passage 20 isleft open to compensate this reduced pressure.

Furthermore, after the liquid substance has been filtered, residualquantities of filtrates remain in the suction chamber, between themembrane 36 and the reception surface, with the result that the membraneremains moist. The microorganisms tend to diffuse when the moistmembrane is placed on the culture medium.

Accordingly, before removing the filter unit 34 from the reception head14, the passage 20 is opened by moving the valve 26 into the secondposition, so that sterile external air can be aspirated via the suctionduct 18. As a result, the aspirated air tends to dry the suction chamberand therefore the membrane 36.

Moreover, connecting means, not shown, are provided in the perimeter ofthe end 22 of the passage 20 that discharges externally of the receptionhead 14 for the connection thereto of a supply of cleaning liquid, forexample.

The passage 20 is obviously closed during filtration, on the one hand sothat the reduced pressure in the suction chamber is sufficient toaspirate the liquid substance through the membrane 36 and on the otherhand to prevent the liquid substance leaking out of the reception head14.

A particularly advantageous embodiment of the invention in which thereception head 14 is removably mounted on the head support 12 isdescribed next with reference to FIG. 3.

FIG. 3 shows the reception head 14 disposed opposite the head support12, on which it is adapted to bear.

To this end, the reception head 14 has an axial opening 42 in its lowerwall 44 adapted to receive a projecting vertical portion 46 of the headsupport 12. The suction duct 18 discharges directly into the axialopening 42.

The suction branch 19 extends longitudinally in the projecting verticalportion 46 and its first end is intended to be connected, at one end 48of the projecting vertical part 19, to the suction duct 18 of thereception head 14 when the latter is mounted on the head support 12.

The second end of the suction branch 19 is connected to a vacuummanifold or to a suction pump, not shown, to aspirate the liquidsubstance contained in the filter unit 34 through the membrane 36.

It is necessary for the connection between the suction branch 19 and thesuction duct 18 to be sealed to prevent liquid substance or air leaks.To this end, the projecting vertical portion 46 and the axial opening 42of the reception head 14 are circular cylinders so that seals 50 caneasily be inserted.

The projecting vertical portion 46 also has a first shoulder 52 againstwhich a corresponding second shoulder 54 of the reception head 14 isadapted to bear. As a result the reception head 14 is adapted to beprevented from movement in translation in at least one direction, towardthe head support 12.

The projecting vertical portion 46 also has a groove 56 into which keymeans 58 mounted in said reception head 14 are adapted to be extended.

The key means 58 are described with reference to FIG. 4, which is a viewof the reception head 14 shown in FIG. 1 in section taken along the lineIV-IV.

FIG. 4 shows the axial opening 42 and the key means 58, which are mobilein translation in a lateral bore 60 formed in the reception head 14 anda portion 62 of which intersects the axial opening 42.

The key means 58 comprise a rod with a portion 64 whose section issubstantially equal to the section of the transverse bore 60 and aportion 66 that forms an elongate groove.

As shown in FIG. 4, the portion 64 of the key means 58 intersects theaxial opening 42 with the result that this portion is able to be engagedin the groove 56 of the projecting vertical portion 46 of the headsupport 12 and thereby connect together the projecting vertical portion46 and the reception head 14. When the key means 58 are actuated in thedirection of the arrow F, a return spring 57 is compressed and theportion 66 is moved opposite the axial opening 42, but does notintersect said axial opening 42, with the result that it is fully openand the reception head 14 can be mounted on the head support 12 orremoved therefrom without impediment.

Clearly, when the key means 58 are released, the return spring 57returns the portion 64 to its original position and movement intranslation of the key means 58 in the direction opposite that of thearrow F is prevented by a stop.

A removable reception head 14′ in accordance with another embodiment andadapted to be mounted on a head support identical to the head supportpreviously described is described next with reference to FIGS. 5, 6 and7.

FIG. 7 shows the reception head 14′ positioned above the head support 12with the projecting vertical portion 46 and the punch 30 of the core ofthe solenoid 28.

The reception head 14′ has a reception surface 16′ surrounded by acircular rim 70 against the internal wall of which bears an O-ring 72lodged in a groove. Accordingly, in this embodiment, a different type offilter unit can be mounted on the reception head 14′, the base of saidfilter unit being nested in the head and bearing against the wall of thecircular rim 70 and against the O-ring 72 to provide the seal.

Filter units of the above kind are used when the membrane must be spacedfrom the reception surface 16′ to prevent contamination.

Accordingly, different types of filter unit can be used with the samedevice including a head support 12, different reception heads beingadapted to receive the different filter units.

To this end, the filter heads all comprise the same base adapted to bemounted on the head support 12. As explained with reference to FIG. 6,the reception head 14′ includes connecting means identical to those ofthe reception head 14 shown in FIG. 4.

FIG. 6 shows the reception head 14′ with its circular rim 70 around thereception surface 16′ and its internal wall fitted with the O-ring 72.Furthermore, the reception head 14′ comprises key means 58 entirelysimilar to those of the reception head 14 shown in FIG. 4 and adapted tocooperate with the projecting vertical portion 46 of the head support 12in the same way.

FIG. 5 is a vertical axial section of the reception head 14′ shown inFIG. 7, and shows a passage 20′, one end 22′ of which dischargesexternally of the reception surface 16′ and externally of the receptionhead 14′, and the other end 24′ of which discharges onto the receptionsurface 16′. In FIG. 5, the passage 20′ is closed by a valve 26′ in afirst position and consisting of a piston similar to that shown in FIG.1.

The structure and the operation of the valve 26′ are identical to thoseof the valve 26 shown in FIGS. 1 and 2 in order to produce the sameresult.

The reception heads 14, 14′ described hereinabove are made of solidheat-resistant materials that are also resistant to powerfuldisinfecting agents, so that they can be sterilized at temperaturesabove 120° C., for example 134° C., and/or by immersion in chlorinatedsolutions, for example.

The materials used are ideally stainless steels, for example 316Lstainless steel, or plastics materials, for example PEEK.

The seals are made from elastomer type plastics materials, for examplepolyurethane, which resist heat treatment and sterile solutions.

The present invention is in no way limited to the embodiments describedand shown, which the person skilled in the art will know how to modifywithin the spirit of the invention.

1. A mechanical support for a drainage device of a filter unit adaptedto be mounted on said mechanical support wherein said mechanical supportcomprises: (1) a reception head including a reception surface and anexternal surface portion, wherein said reception head is adapted toreceive said filter unit; (2) a passage, one end of which dischargesexternally of said reception surface facing a membrane provided in thefilter unit and the other end of which discharges onto said receptionsurface; (3) selectively operable closure means, movable between a firstposition to close said passage and a second position to open saidpassage, wherein said selectively operable means comprises a valveadapted to slide in a bore which discharges onto said external surfaceportion of said reception head; and (4) a driver device adapted to bearagainst said valve to drive it in translation into said first positionor into said second position, wherein said passage is opened or closedby operating said valve from outside said reception head.
 2. Themechanical support according to claim 1, wherein said support furthercomprises a suction duct that discharges onto said reception surface,thereby to aspirate a liquid substance contained in said filter unitthrough said membrane.
 3. The mechanical support according to claim 1,wherein said mechanical support further comprises first connecting meansand a head support including second connecting means, said receptionhead being adapted to be mounted on said head support so that the firstconnecting means and the second connecting means cooperate with eachother.
 4. The mechanical support according to claim 3, wherein saidfirst connecting means is formed by a cylindrically symmetric opening insaid reception head formed in a portion opposite said reception surfaceand said second connecting means is formed by a substantially verticalprojecting portion in said head support and is adapted to cooperate withsaid opening when mounting said reception head on said head support. 5.The mechanical support according to claim 3, wherein said reception headand said head support include keying means for locking said first andsecond connecting means.
 6. The mechanical support according to claim 3,wherein said reception head has a transverse bore adapted to cooperatewith a groove formed around said vertical projecting portion, saidtransverse bore being adapted to receive key means comprising a rod forforming keying means.
 7. The mechanical support according to claim 2,wherein said head support includes a suction branch having a first endadapted to be connected to said suction duct of said reception head anda second end adapted to be connected to a suction pump.
 8. Themechanical support according to claim 1, wherein said driver device isadapted to take up a position opposite said external surface portion. 9.The mechanical support according to claim 8 wherein said driver deviceincludes a solenoid whose core is adapted to drive said valve.
 10. Themechanical support of claim 6, wherein the rod comprises one portioncomprising a section substantially equal to the section of saidtransverse bore and a second portion comprising an elongate groove. 11.A reception head comprising a reception surface and adapted to receive afilter unit, wherein said reception head comprises: (1) a passage, oneend of which discharges externally of said reception surface and theother end of which discharges internally of said reception surface; (2)selectively operable means for closing said passage, movable between afirst position to close said passage and a second position to open saidpassage, wherein said selectively operable means comprises a valveadapted to slide in a bore which discharges onto an external surfaceportion of said reception head and wherein the valve is operated fromoutside of said reception head; (3) a cylindrically symmetric openingformed in a portion opposite said reception surface; and (4) atransverse bore adapted to cooperate with said opening, said transversebore being adapted to receive key means comprising a rod for formingkeying means.
 12. The mechanical support of claim 11, wherein the rodcomprises one portion comprising a section substantially equal to thesection of said transverse bore and a second portion comprising anelongate groove.
 13. A mechanical support for a drainage device of afilter unit adapted to be mounted on said mechanical support whereinsaid mechanical support comprises: (1) a passage, one end of whichdischarges externally of a reception surface facing a membrane providedin the filter unit and the other end of which discharges onto saidreception surface; (2) selectively operable closure means, movablebetween a first position to close said passage and a second position toopen said passage, wherein said selectively operable means comprises avalve adapted to slide in a bore which discharges onto an externalsurface portion of a reception head to drive said valve in translationbetween said first position and said second position; and (3) areception head comprising a transverse bore adapted to cooperate with agroove formed around said vertical projecting portion, said transversebore being adapted to receive key means comprising a rod for formingkeying means.